[BUILD] New FET/RACK Official Help Thread - Please read first post!

[Echo North]

So I checked all of the L brackets and they seem to be all tight and good to go. I rechecked all the grounding points and I think I fixed an issue because now I am reading the correct 30VDC from the chassis to CR8. But now I'm only reading a couple of millivolts from the chassis to CR9. What could be causing that?

Could be a million things.  Are R81 and R82 soldered correctly? Is R9 installed in the correct direction? R9 could be dead, you could remove it and test it with your diode tester on your DMM.

Mike

 

[alex_dempsey]

So I checked all of the L brackets and they seem to be all tight and good to go. I rechecked all the grounding points and I think I fixed an issue because now I am reading the correct 30VDC from the chassis to CR8. But now I'm only reading a couple of millivolts from the chassis to CR9. What could be causing that?

In addition, is it possible that I blew up CR9 while running that extra voltage to it? If I'm doing the diode test correctly, its reading nothing at all which would mean its bad. The other diodes on the board give me a reading when using the same test.

 

[Echo North]

In addition, is it possible that I blew up CR9 while running that extra voltage to it? If I'm doing the diode test correctly, its reading nothing at all which would mean its bad. The other diodes on the board give me a reading when using the same test.

Ya you should see OL in one direction, and the voltage drop (0.7ish) in the other direction.  If you get OL in both directions it's probably dead.

We can send you one if you send us an email.

Mike

 

[rubberband]

Still trying to get time. However, I think if you increase those 4 resistors by 10x you'll get what you want. So 56K change to 560K and so on. Just like you said.

Report back!

Mike

Found the time to replace, works great, I am able to work with hot sources much more effectively! Would highly recommend the mod.

 

[Echo North]

Found the time to replace, works great, I am able to work with hot sources much more effectively! Would highly recommend the mod.

Nice!

Yup it's pretty straight forward. You're just lowering the level of the audio entering the side chain a little.

Mike

 

[alex_dempsey]

Could be a million things.  Are R81 and R82 soldered correctly? Is R9 installed in the correct direction? R9 could be dead, you could remove it and test it with your diode tester on your DMM.

Mike

Sorry about the delay. So I've corrected the issue with the power supply and it is functioning correctly now. But when doing the calibration process, my Q-Bias trimmer still is not having any effect on the voltage readings. Any ideas what might be causing that?

Alex

 

[Echo North]

Sorry about the delay. So I've corrected the issue with the power supply and it is functioning correctly now. But when doing the calibration process, my Q-Bias trimmer still is not having any effect on the voltage readings. Any ideas what might be causing that?

Alex

Go through this again and report back what is out of spec:
http://www.hairballaudio.com/blog/resources/post/fetrack-troubleshooting-guide

 

[alex_dempsey]

Go through this again and report back what is out of spec:
http://www.hairballaudio.com/blog/resources/post/fetrack-troubleshooting-guide

I checked out the troubleshooting page and it wasn't much help. It told me to check the the test point for the Q-Bias and now I am reading the correct thing at that test point. Like I said earlier, I'm still concerned that the meter is pinned to the right any time I turn the circuit on to gain reduction. The power supply is definitely functioning properly now but I'm not getting the right readings when measuring the two test points on the output XLR. Its only reading a few millivolts instead of a few volts. In the past, I got it to read the correct thing but since changing a blown diode (from having too much voltage run through the circuit) those two output test points aren't reading the correct thing. Any ideas of what to try next??

 

[Echo North]

I checked out the troubleshooting page and it wasn't much help. It told me to check the the test point for the Q-Bias and now I am reading the correct thing at that test point. Like I said earlier, I'm still concerned that the meter is pinned to the right any time I turn the circuit on to gain reduction. The power supply is definitely functioning properly now but I'm not getting the right readings when measuring the two test points on the output XLR. Its only reading a few millivolts instead of a few volts. In the past, I got it to read the correct thing but since changing a blown diode (from having too much voltage run through the circuit) those two output test points aren't reading the correct thing. Any ideas of what to try next??

With those symptoms there will be clear errors in your voltage readings. You need to start going through that guide and tell me where it's off.  I can't magically tell you what is wrong.  Going through those steps in the guide will help me locate the issue.

Go through the readings for 1-5 in that guide. Report back.

Mike

 

[alex_dempsey]

With those symptoms there will be clear errors in your voltage readings. You need to start going through that guide and tell me where it's off.  I can't magically tell you what is wrong.  Going through those steps in the guide will help me locate the issue.

Go through the readings for 1-5 in that guide. Report back.

Mike

So I've fixed the output reading so its reading the correct thing. Now the first issue I run into is during the Q-Bias calibration. I got it to read the 2.75VAC that it asks for. All of the settings are correct on the front panel. When I turn the Q-Bias down, it doesn't change the voltage reading at all. Every step before that point is currently functioning properly.

Alex

 

[Echo North]

So I've fixed the output reading so its reading the correct thing. Now the first issue I run into is during the Q-Bias calibration. I got it to read the 2.75VAC that it asks for. All of the settings are correct on the front panel. When I turn the Q-Bias down, it doesn't change the voltage reading at all. Every step before that point is currently functioning properly.

Alex

Step one in the guide is testing pad 18, which is the Qbias.  What are your readings?

 

[alex_dempsey]

Step one in the guide is testing pad 18, which is the Qbias.  What are your readings?

I am reading -1.7 VCD at the test point for the Q-Bias.

 

[Echo North]

I am reading -1.7 VCD at the test point for the Q-Bias.

Look at that again, you should be getting 2 readings, one at each end of the trimmer.

 

[alex_dempsey]

Look at that again, you should be getting 2 readings, one at each end of the trimmer.

At full CW the right point on the Q-Bias is flashing between about 4V and .5 V. The other point is reading less than a millivolt.

 

[Echo North]

At full CW the right point on the Q-Bias is flashing between about 4V and .5 V. The other point is reading less than a millivolt.

So pad 18 is -1.7 VDC on one end of the Qbias trimmer and between what on the other side? 4VDC?

Are you sure your ground reference is right and your meter isn't broken or you have it set wrong?

We're measuring for DC.

 

[alex_dempsey]

So pad 18 is -1.7 VDC on one end of the Qbias trimmer and between what on the other side? 4VDC?

Are you sure your ground reference is right and your meter isn't broken or you have it set wrong?

We're measuring for DC.

Woah measuring AC before sorry about that!

Between case ground and one point was reading -1.775VDC and -.935VDC on another end. The top of the triangle is also reading -1.775VDC.

 

[Echo North]

Woah measuring AC before sorry about that!

Between case ground and one point was reading -1.775VDC and -.935VDC on another end. The top of the triangle is also reading -1.775VDC.

Alright now do step 2 in the guide and report back...that is AC.

 

[Echo North]

Set that QBias to -1.775 DC before doing step 2.

 

[alex_dempsey]

Alright now do step 2 in the guide and report back...that is AC.

TP15 is reading 4.8VAC.
TP17 is reading about .5VAC.
TP1 is reading about .17VAC.

 

[Echo North]

TP15 is reading 4.8VAC.
TP17 is reading about .5VAC.
TP1 is reading about .17VAC.

What about the output between + and -    ?

Mike